1. Field of Invention
This invention relates to saggers, and, more particularly, to a sagger construction particularly adapted for stacking cylindrical articles to be fired such as spark plugs in a vertical orientation.
2. Description of the Prior Art
Because of the thermal stresses to which saggers are subject by repeated firings often under rapid heating and cooling cycles, the design of a sagger is usually maintained relatively simple. Most saggers are of a topless square or rectangular configuration. Sometimes, when multiple layers are fired, saggers are constructed with a first sagger having a bottom wall and other saggers to be stacked vertically on top of the first sagger are constructed without a bottom wall so that the saggers can be successively loaded. Some saggers have a bottom which can be removed for rapid discharge of the fired articles.
When generally elongated bodies are fired such as cylindrical parts or rectangular parts, for example, tool bits or spark plugs, maximum loading is facilitated by utilizing a packingg material within the sagger to maintain the parts upright, that is, with their axis in a vertical position. The use of packings or alternatively inserts such as those that have an egg-crate appearance, helps to maintain the parts in a vertical position until they have been fired and allows maximum density placement of the parts within the saggers. Usually the packing or inserts are burned away during the firing process so that the parts fall over in a random orientation during the firing process. This sometimes causes breakage of the parts during the firing or the unloading process. Also, while a packing or an insert allows the parts to be properly oriented, they do not lend themselves to use with automatic loaders such as those shown in my U.S. Pat. Nos. 4,550,551 and 4,594,839. A high degree of success has been obtained by utilizing the loading mechanism described and shown in the foregoing patents. Typically the automatic loader is used with such articles as rectangular carbide cutting inserts and the like which are packed in a series of horizontal rows with the axis of the parts being maintained generally vertical. This invention is directed primarily to an improvement in a rectangular sagger construction for use with loaders that load parts singly or a row of parts at a time or to facilitate the manual loading of parts particularly cylindrical parts which can be nested within each other in the loading process.